Valine is useful as a starting material for pharmaceutical amino acid preparations, as a synthetic intermediate for various pharmaceutical preparations and as an intermediate for chemicals such as agricultural chemicals.
Leucine is useful as a starting material for pharmaceutical amino acid preparations, nutrients, and as a synthetic intermediate for various pharmaceutical preparations.
Isoleucine is useful as a starting material for pharmaceutical amino acid preparations, nutrients, and as a synthetic intermediate for various pharmaceutical preparations.
In general, valine, leucine and isoleucine are generically called branched chain amino acids.
Valine is produced by hydrolyzing proteins such as soybean protein or by a method of culturing a microorganism having the ability to produce valine. The conventional methods of isolating and purifying valine from aqueous, valine-containing solutions such as protein hydrolysates, fermentation broth etc. obtained in these methods include:
(1) a method of removing neutral amino acids other than valine by repeatedly re-crystallizing the neutral amino acid fraction collected by separating and removing from acidic and basic amino acids by treatment with ion exchange resins (Biochem. J., 48, 313 (1951)); and
(2) a method of adding hydrochloric acid to an aqueous solution containing valine and then repeatedly forming and precipitating crystals of valine hydrochloride (Japanese Patent Application Laid-Open Publication No. 16450/81). However, there are the problems that the former method is very cumbersome in operation and difficult to separate valine from leucine and isoleucine, while the latter results in lower yield because of the high solubility of crystals of valine hydrochloride in water.
Other valine purification methods include precipitating an adduct (slightly soluble salt) selectively with valine. For example, tetrachloro-orthophthalic acid, sulfoisophthalic acid, flavian (phonetic) acid amenol "flavianic acid" (Japanese Patent Publication No. 25059/67), or p-isopropylbenzenesulfonic acid (Japanese Patent Application Laid-Open Publication No. 333,312/96), is allowed to form an adduct with valine in order to purify valine. However, there are the problems that the precipitants used for valine: tetrafluorophthalate, sulfoisophthalate, and flavianate, are expensive and hard to obtain industrially, and the solubility of the resulting adduct is so high that recovery of valine in high yield is difficult so these methods of isolating valine from the adduct are cumbersome. On the other hand, p-isopropylbenzenesulfonic acid is very effective as a precipitant for valine, but there are the problems that p-isopropylbenzenesulfonic acid itself is not capable of decomposition with active sludge, so disposal of its waste fluid is difficult. Because of its hard formation of a sparingly soluble salt with isoleucine, it cannot be applied to other branched chain amino acids and so its use is limited.
Leucine is produced by a method of hydrolyzing proteins such as soybean protein or by a method of culturing a microorganism having the ability to produce leucine. The conventional methods of isolating and purifying leucine from aqueous, leucine-containing solutions such as protein hydrolysates, fermentation broth obtained in these methods include:
(1) a method of removing neutral amino acids other than leucine by repeatedly re-crystallizing the neutral amino acid fraction collected by separating and removing acidic and basic amino acids by treatment with ion exchange resins (Biochem. J., 48, 313 (1951)); and
(2) a method of adding hydrochloric acid to an aqueous solution containing leucine and then repeatedly forming and precipitating crystals of leucine hydrochloride (Experimental Chemistry Lecture, Vol. 23, Biochemistry I, 75, compiled by the Chemical Society of Japan and published by Maruzen (1957)). However, there are the problems that the former is very cumbersome in operation and it is difficult to separate leucine from valine and isoleucine, while the latter results in lower yield because of the high solubility of crystals of leucine hydrochloride in water.
Other leucine purification methods include precipitating an adduct (slightly soluble salt) selectively with leucine. For instance, naphthalene .beta.-sulfonic acid, 2-bromotoluene-5-sulfonic acid (Experimental Chemistry Lecture, Vol. 23, Biochemistry I, 75, compiled by the Chemical Society ol Japan and published by Maruzen (1957)), 1,2-dimethylbenzene-4-sulfonic acid (Japanese Patent Application Laid-Open Publication No. 11373/65), benzenesulfonic acid (Japanese Patent Application Laid-Open Publication No. 149,222/76), or p-toluenesulfonic acid (Japanese Patent Application Laid-Open Publication No. 3016/77), is allowed to form art adduct with leucine in order to purify leucine. However, there are the problems that the precipitants used for leucine naphthalene P-sulfonate and 2-bromotoluene-5-sulfonate are expensive and hard to obtain industrially, and the solubility of the resulting adduct is so high that recovery of leucine in high yield is difficult, and the method of isolating leucine from the adduct is cumbersome. On the other hand, 1,2-dimethylbenzene-4-sulfonic acid, benzene sulfonic acid and p-toluenesulfonic acid are very effective as precipitants for leucine, but 1,2-dimethylbene-4-sulfonic acid hardly forms a slightly soluble salt with valine and isoleucine; benzene sulfonic acid hardly forms a slightly soluble salt with isoleucine; and p-toluenesulfonic acid hardly forms a sparingly soluble salt with valine, so their limited use is disadvantageous.
Isoleucine is produced by a method of hydrolyzing proteins, such as soybean protein or by a method of culturing a microorganism having the ability to produce isoleucine. The conventional methods of isolating and purifying isoleucine from aqueous, isoleucine-containing solutions such as protein hydrolysates and fermentation broth obtained in these methods include:
(1) a method of removing neutral amino acids other than isoleucine by repeatedly re-crystallizing the neutral amino acid fraction collected by separating and removing acidic and basic amino acids by treatment with ion exchange resins (Biochem. J., 48, 313 (1951)); and
(2) a method of adding hydrochloric acid to an aqueous solution containing isoleucine and then repeatedly forming and precipitating crystals of isoleucine hydrochloride (J. Biologc. Chem., 118, 78 (1973)). However, there are the problems that the former method is very cumbersome in operation and difficult to separate isoleucine from valine and leucine, while the latter method results in lower yield because of the high solubility of crystals of isoleucine hydrochloride in water.
Other isoleucine purification methods include precipitating an adduct (sparingly soluble salt) selectively with isoleucine. For instance, 4-nitro-4'-methyldiphenylamine-2-sulfonic acid (J. Biologc. Chem., 143, 121 (1942)), 2-naphthol-6-sulfonic acid (Japanese Patent Application Laid-Open Publication No. 13515/73), or 1,5-napthalenedisulfonic acid (Japanese Patent Application Laid-Open Publication No. 109,953/79), is allowed to form an adduct in order to purify isoleucine. However, there are the problems that the precipitants are expensive and hard to obtain industrially, the method of isolating isoleucine from the adducts is cumbersome, difficult formation of salts with amino acids other than isoleucine makes their usage limited, and the toxicity of the precipitants themselves is high.